"The Afghan people are clearly eager to participate in elections that will help them move away from the rule of the gun," said Sam Zarifi, deputy director of the Asia Division of Human Rights Watch.

But there is a "an underlying climate of fear among many voters and candidates, especially in remote, rural areas," the New York-based rights group said in a statement.

Taliban rebels have stepped up attacks in the lead-up to the polls, and fighting has left more than 1,200 people dead.

Sunday's elections are the final formal step toward democracy on a path laid out after U.S.-led forces ousted the Taliban in 2001. Presidential elections last October entrenched Hamid Karzai as the nation's leader.

Some 2,775 candidates - including 335 women - are competing for the 249 National Assembly seats, a quarter of which are reserved for women, while 3,025 candidates are vying for local assemblies in all 34 provinces.

"Technical preparations for the election have been largely successful and the polls will likely take place without serious disruption although attacks by insurgent forces could derail voting in some areas," the rights group said.

It urged the government and international security forces to "redouble efforts to improve security and human rights protections during and after the elections."

The group also expressed concern that some nations may pull their forces out of Afghanistan shortly after the vote, the AP reports.